PDBsum entry 4hhm

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Isomerase PDB id
Protein chains
(+ 2 more) 386 a.a.
_MG ×8
_CO ×8
Waters ×2357
PDB id:
Name: Isomerase
Title: Crystal structure of a mutant, g219a, of glucose isomerase f streptomyces sp. Sk
Structure: Xylose isomerase. Chain: a, b, c, d, e, f, g, h. Engineered: yes. Mutation: yes
Source: Streptomyces sp. Sk. Organism_taxid: 253732. Gene: xyla. Expressed in: escherichia coli. Expression_system_taxid: 562.
2.15Å     R-factor:   0.197     R-free:   0.250
Authors: H.Ben Hlima,J.Riguet,R.Haser,N.Aghajari
Key ref: H.Ben Hlima et al. (2013). Identification of critical residues for the activity and thermostability of Streptomyces sp. SK glucose isomerase. Appl Microbiol Biotechnol, 97, 9715-9726. PubMed id: 23463249 DOI: 10.1007/s00253-013-4784-2
10-Oct-12     Release date:   27-Mar-13    
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Protein chains
Pfam   ArchSchema ?
Q9ZAI3  (Q9ZAI3_9ACTO) -  Xylose isomerase
388 a.a.
386 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 1 residue position (black cross)

 Enzyme reactions 
   Enzyme class: E.C.  - Xylose isomerase.
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: D-xylopyranose = D-xylulose
= D-xylulose
      Cofactor: Mg(2+)
Molecule diagrams generated from .mol files obtained from the KEGG ftp site
 Gene Ontology (GO) functional annotation 
  GO annot!
  Cellular component     cytoplasm   1 term 
  Biological process     carbohydrate metabolic process   3 terms 
  Biochemical function     isomerase activity     4 terms  


    Key reference    
DOI no: 10.1007/s00253-013-4784-2 Appl Microbiol Biotechnol 97:9715-9726 (2013)
PubMed id: 23463249  
Identification of critical residues for the activity and thermostability of Streptomyces sp. SK glucose isomerase.
H.Ben Hlima, S.Bejar, J.Riguet, R.Haser, N.Aghajari.
The role of residue 219 in the physicochemical properties of D-glucose isomerase from Streptomyces sp. SK strain (SKGI) was investigated by site-directed mutagenesis and structural studies. Mutants G219A, G219N, and G219F were generated and characterized. Comparative studies of their physicochemical properties with those of the wild-type enzyme highlighted that mutant G219A displayed increased specific activity and thermal stability compared to that of the wild-type enzyme, while for G219N and G219F, these properties were considerably decreased. A double mutant, SKGI F53L/G219A, displayed a higher optimal temperature and a higher catalytic efficiency than both the G219A mutant and the wild-type enzyme and showed a half-life time of about 150 min at 85 °C as compared to 50 min for wild-type SKGI. Crystal structures of SKGI wild-type and G219A enzymes were solved to 1.73 and 2.15 Å, respectively, and showed that the polypeptide chain folds into two structural domains. The larger domain consists of a (β/α)8 unit, and the smaller domain forms a loop of α helices. Detailed analyses of the three-dimensional structures highlighted minor but important changes in the active site region as compared to that of the wild-type enzyme leading to a displacement of both metal ions, and in particular that in site M2. The structural analyses moreover revealed how the substitution of G219 by an alanine plays a crucial role in improving the thermostability of the mutant enzyme.